Excavation equipment with excavation buckets for digging and grading has been known for many years. The buckets themselves have been developed and refined over the years to increase the digging efficiency of such devices. Excavation buckets are typically adapted to backhoes. A backhoe is a type of excavation equipment which includes, generally, a tractor and an articulating, hinged arm assembly attached to the tractor. The arm assembly is mechanically interconnected at one end to the tractor and at its opposing end to an excavation bucket. In use, the bucket is extended away from the tractor, engaged with the material being excavated, and then drawn toward the tractor to scoop the material into the bucket.
A typical excavation bucket comprises, generally, a pair of spaced-apart side plates and a bottom plate joined along edge portions of the side plates to define a material-containing volume therein. A leading edge of the bucket, defined by the leading edge of the bottom plate, may be provided with a plurality of teeth for improved digging action. The rear of the bucket is provided with mounting plates defining holes for mounting the bucket onto the arm of a backhoe.
In this conventional configuration, the bottom plate of the bucket is a continuous plate extending from the front of the bucket to the rear of the bucket. The profile of the bottom plate is typically arcuate, defining a varying radius of curvature along different portions of the bottom plate. During use, the bucket is rotated by the backhoe arm while the leading edge of the bucket is forced into the material being excavated. The configuration of the bottom plate, and of the bucket generally, is such that the bottom plate slides relative to the material and provides little resistance to movement of the bucket. The leading edge of the bucket, at which the teeth are located, is typically the widest transverse portion of the bucket and the portion of the bucket that extends deepest into the trench. This configuration insures that there will be little or no interference between the bucket side plates and the sidewalls of the excavated trench or ditch.
Backhoes are particularly effective for digging trenches and ditches. However, the conventional backhoe bucket becomes difficult to operate when working near building foundations or other locations where buried building service conduits and pipes may extend from the building near the location of excavation. For example, electrical cables, either direct-buried or disposed in buried conduits, water mains, and gas lines, are often buried in the ground adjacent building foundations. When excavating with a conventional bucket near locations known or suspected to include buried objects, it becomes necessary to remove only shallow layers of material as the depth of the trench approaches the buried depth of the buried object. Failure to excavate with caution near the buried object could result in the excavation bucket snagging, rupturing, or otherwise damaging the structure, possibly with catastrophic consequences.
Further, when laying pipe or other conduit in excavated trenches, the final grading of the trench must be carefully and precisely made to ensure proper slope and foundation for the pipe or conduit. This type of operation is difficult to perform with a conventional backhoe bucket because the toothed leading edge of the bucket is not designed to remove shallow layers of excavation material or to permit fine-grading of material to be excavated.